1) Field of the Invention
This invention relates generally to the fabrication of contact openings for a semiconductor device and more particularly to a method of etching and descuming to form a contact opening in an insulating layer for a self-aligned contact in a semiconductor device.
2) Description of the Prior Art
In the manufacture of semiconductor devices, it is normally necessary to make contact to device regions on the substrate surface through an overlying dielectric layer. This is accomplished by first forming an opening or via (contact via) in the dielectric layer over the region to be contacted, and next filling the contact via with a conductive material. The opening is often formed by using a plasma etch. After the etch, photoresist is removed by ashing using a plasma. Etching using a plasma is an indispensable technique in etching a micropattern of an integrated circuit.
In addition to filling the vias with a conductive material, it is necessary to electrically connect certain device regions with others, as well as to provide for electrical connection to external leads. Theses requirements are met by forming a wiring layer over the surface of the substrate. The wiring layers are formed by depositing a conductive material on top of the dielectric layer in which the vias have been formed. The conductive layer is then masked and etched to leave continuous lines of conductive material necessary to match the appropriate connections to the device regions of the substrate. These lines are known as interconnects.
As device geometries have shrunk to submicron levels and devices have become more densely packed on the substrate surface, the aspect ratio (ratio of height to width) of the contact opening to the device regions has greatly increased. The sharp angled surface has caused problems with metal adhesion to the insulating layer.
Moreover, conventional contact opening processes are complicated, require many process steps and do not adequately remove polymer and photoresist residue from the contact openings. This reduces yields and increases contact resistance.
Many solutions have been tried without satisfactory success to reduce the process complexity and eliminate the polymer/precipitation problem. U.S. Pat. No. 5,397,432 (Konno et al.) shows a method and apparatus for plasma etching Al metal and ashing. The ashing operation has H.sub.2 O added. The asher is connected to the RIE etcher. U.S. Pat. No. 5,468,686 (Kawamoto) shows a method of cleaning a chamber of a dry etching system. U.S. Pat. No. 5,284,547 (Watanabe) teaches a plasma-process system with a batch scheme-ashing and etching are performed. However, there is still a need for an improved descum process that reduces cycle time and eliminates process steps.